Merit (meritum), as we have explained in the first part of this treatise,(1221) is that property of a good work which entitles the doer to a reward (praemium, merces).
Ethics and theology distinguish two kinds of merit: (1) condign merit or merit in the strict sense of the term (meritum adaequatum sive de condigno), and (2) congruous merit or quasi-merit (meritum inadaequatum sive de congruo). Condign merit supposes an equality between service and return. It is measured by commutative justice and confers a strict claim to a reward. Congruous merit, owing to its inadequacy and the lack of strict proportion between service and recompense, confers no such claim except on grounds of equity.(1222)
In this treatise we are concerned with merit only in the theological sense of the term, i.e. supernatural merit. We shall consider (1) its Existence,(1223) (2) its Requisites,(1224) and (3) its Objects.(1225)